The invention relates to weapon systems comprising a weapon and an aiming system and is especially, but not exclusively, applicable to weapons which employ superelevation of the barrel, such as grenade machine guns.
For some weapons, such as grenade launching machine guns, which fire relatively slow, heavy rounds, it is necessary to elevate the barrel by a relatively large angle, perhaps 30 degrees or more, above the sight line to the target. It is desirable to maintain the target image in view throughout the engagement to compensate for target changes, motion or other dynamic events. Modern weapons use sights with a high magnification to obtain precision aiming at large ranges. Such sights have a field of view of only a few degrees, increasing the likelihood that the user will lose sight of the target during xe2x80x9csuperelevationxe2x80x9d of the barrel.
One known aiming system, known as the Small Arms Module Fire Control System (SACMFCS) by Contraves Inc., has the sight mounted upon a motorized tilting platform. Once the target has been ranged and the aiming point displaced downwards according to the computed superelevation, the motorized platform is driven to tilt the sight downwards a corresponding amount. The target then is out of the field of view, so the operator raises both the barrel and the sight until the target is in view again. The system is not entirely satisfactory because the target is lost from view during superelevation, and because precision, speed of operation, and ruggedness are required, tending to make a suitable motor drive large and expensive. Also, the platform increases the height of the display above the barrel, so the operator""s head is exposed more than is desirable.
U.S. Pat. No. 4,193,334 (Jackson) issued Mar. 18, 1980 discloses a sight coupled to the weapon""s barrel by way of a slip clutch so that the sight moves with the barrel during superelevation of the latter. The slip clutch allows the user to depress the sight relative to the gun barrel so as to view the impact of the round, and then return the sight to alignment with the gun barrel. However, the user still loses sight of the target while the gun barrel is being superelevated. Now that laser rangefinders are common, the target may be able to detect that it has been targeted by a laser rangefinder and take evasive action. It is important, therefore, to minimize the time taken between ranging the target, superelevating the gun barrel, and firing the gun. It is also desirable to minimize the time taken to select and fire at a series of targets in quick succession. Jackson""s gun would be relatively slow because, not only must the sight be depressed to view the target, but it must then be returned manually to alignment with the barrel. During the time taken to superelevate the gun barrel and depress the sight to view the target again, the target might have moved, leading to inaccuracies. A further disadvantage is that the amount of superelevation is set by means of manually adjustable slides or scales.
U.S. Pat. No. 5,686,690 (Lougheed et al) issued November 1997 and commonly owned with the present invention, describes a weapon having a barrel and a sight mounted upon a support which can be rotated in azimuth but not in elevation. The gun barrel can be elevated relative to the support, but the sight cannot. Consequently, the sight remains trained on the target during the superelevation step. To change the field of view of the sight in elevation, however, the tripod must be adjusted or repositioned, which is awkward and time-consuming. A further disadvantage is that the rangefinder is mounted upon the gun barrel. Consequently, in order to range a new target, the user must depress the gun barrel until it is pointing directly at the new target again. Once the new target has been ranged, the gun barrel must be superelevated again. This is not satisfactory when there are multiple, fast-moving targets relatively close to each other. Yet another disadvantage is that the rangefinder and the sight must be boresighted to the gun barrel separately, which is time-consuming and makes it more difficult to obtain and maintain precise calibration.
One object of the present invention seeks to eliminate, or at least mitigate, the disadvantages of the above-mentioned weapon sights and to provide an improved weapon sight arrangement which permits the operator to view the target during superelevation of the weapon.
According to one aspect of the present invention, there is provided a weapon system comprising a weapon and an aiming system both mounted upon a support, the weapon having a barrel unit and the aiming system comprising:
(i) an imaging unit for providing an image of a scene within a field of view of the imaging unit;
(ii) a display unit for displaying the image;
(iii) the coupling unit having a first operational state in which the coupling unit fixes the imaging unit relative to the support while allowing elevation of the barrel unit relative thereto and a second, alternative state in which the coupling unit entrains the imaging unit to move with the barrel unit relative to the support,
(iv) angle encoding means for providing a displacement signal representing displacement of the imaging unit in elevation relative to said first part; and
(v) control means comprising means for controlling the coupling unit to select the first state and the second state alternatively and means responsive to the displacement signal for determining when a required change in elevation of the barrel unit relative to the support with the coupling unit in the first operational state has been effected and causing the display to provide an indication thereof.
The weapon system may further comprise a rangefinder for providing a range of a target in the field of view of the imaging unit, and the control means then may comprise:
a control computer unit comprising means for providing upon the image an aiming reticle representing an aiming point of the barrel once the imaging unit has been boresighted to the barrel unit and a ranging reticle representing an aiming point of the rangefinder, means for controlling the reticle providing means to adjust the position of the aiming reticle in dependence upon the displacement signal, and means for computing a required change in elevation of the barrel unit in dependence upon a range measured the rangefinder and applying a corresponding offset to the displacement signal so as to displace the aiming reticle relative to the field of view in a direction opposite the change.
The aiming system may further comprise means for providing an elevation signal representing displacement of a line of sight of the imaging unit relative to the ground and/or a cant signal representing inclination of the imaging unit relative to the ground. The control computer may take such cant and/or elevation signals into account when computing the required elevation.
According to a second aspect of the invention, there is provided the aiming system per se for mounting onto a weapon to form a weapon system according to the first aspect.
In embodiments of either of the first and second aspects of the invention, where the offset is sufficient to displace the aiming reticle beyond limits in the displayed scene, the control unit may be operable apply a part of the offset to maintain the aiming reticle at a position adjacent a corresponding edge of the field of view and monitor the remaining offset, restoring movement of the aiming reticle with the barrel unit once the barrel unit has been displaced by an elevation angle greater than that corresponding to said remaining offset. The control unit may change the appearance of the aiming reticle while the aiming point is outside the field of view.
The imaging unit may be mounted alongside the barrel unit and coupled to a separate display unit mounted immediately above handles at the rear of the barrel unit for controlling aiming of the weapon. Such an arrangement allows the weapon to have a relatively low profile.
The imaging unit may be completely electronic, such as a CCD sensor unit, or a hybrid of an optical sight with an electronically-controlled superimposed aiming reticle.
In embodiments of either of the foregoing aspects of the invention, the coupling unit may comprise means for fixing the imaging unit relative to the support, specifically a first clutch unit acting between the first part and the second part and engageable to entrain the imaging unit to move with the barrel unit in elevation relative to the support and a second clutch unit acting between the second part and third part and engageable to secure the imaging unit to the support, and switch means for engaging the first clutch unit while simultaneously disengaging the second clutch unit and vice versa.
Alternatively, the coupling unit may comprise a first clutch unit acting between the first part and the second part and engageable to entrain the imaging unit to move in elevation with the barrel unit, and a slip clutch acting continuously between the second part and the third part with sufficient force to retain the imaging unit in fixed elevational relationship with the support, providing the first clutch unit is disengaged, but insufficient force to prevent said movement of the imaging unit when the first clutch unit is engaged.
The means for controlling the coupling unit may comprise a user-operable switch.